Abstract

In this paper we report the detection and mass analysis of negative ions formed in a negative corona discharge using both dry and ‘wet’ air at pressures between 5 and 27 kPa. The yield of individual ions is strongly affected by trace concentrations of ozone, nitrogen oxides and water vapour. In dry air the dominant ion is CO3−. In presence of water this is converted very efficiently to cluster ions containing one and more water molecules. If ozone and nitrogen oxides are added, or are produced in discharge in sufficient concentrations, NO3− ions and NO3− hydrated clusters are formed. Ozone concentrations greater than 25 ppm are sufficient to completely suppress the appearance of O2− ions and its clusters both in dry and wet air. Such observations allow a comprehensive review of the physical and chemical processes within the discharge.